Cap for a writing instrument



FIG. 1 is a perspective view of a cap for a writing instrument showing a new design;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a left view thereof;

FIG. 5 is a right view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The subject matter shown in broken lines is included to show portions of the writing instrument that form no part of the claimed design. 

CLAIM The ornamental design for a “cap for a writing instrument,” as shown and described. 